In a gas turbine, hot gases of combustion flow from an annular array of combustors through a transition piece for flow along an annular hot gas path. Turbine stages are typically disposed along the hot gas path such that the hot gases of combustion flow from the transition piece through first-stage nozzles and buckets and through the nozzles and buckets of follow-on turbine stages. Each turbine bucket generally includes an airfoil extending radially outwardly from a substantially planar platform and a blade root extending radially inwardly from the platform. The blade root of each turbine bucket is generally configured to be received within one of a plurality of circumferentially spaced root slots defined in one of the rotor disks of the turbine rotor, with each rotor disk being mounted to the rotor shaft for rotation therewith.
To improve the overall efficiency of a gas turbine, higher operating temperatures are continuously sought. However, as operating temperatures increase, the high temperature durability of the turbine components must correspondingly increase. Thus, efforts have been made to replace the use of metal in the construction of turbine buckets with the use of ceramic materials, such as ceramic matrix composite materials. As a result, many turbine buckets have been redesigned to accommodate the use of ceramic materials, such as by reshaping the blade root. For example, turbine buckets may now include dovetail-shaped roots as opposed to the fir tree-shaped roots used in metallic buckets. Unfortunately, such reshaping can lead to problems in attaching the blade root to pre-existing rotor disks installed within a gas turbine.
To address such attachment issues, attachment assemblies have been proposed for coupling turbine buckets to rotor disks. However, as of yet, such assemblies have not provided an effective means for axially retaining and/or sealing the turbine bucket within the assembly.
It would also be desirable to remove sealing features from turbine blades. Accordingly, an adaptor assembly for coupling a turbine bucket or blade to a rotor disk that provides for effective axial retention and/or sealing of the turbine blade within the assembly would be desirable.